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(No Model.)

B. P. WARNER & H. H. WAIT. DYNAMO ELECTRIC MACHINE.

No. 587,379. Patented Aug. 3,1897.

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UNITED STATES I PATENT OFFICE.

ERNEST P. WARNER AND-HENRY II. WAIT, OF CHICAGO, ILLINOIS, ASSIGNORS TOTHE IVESTERN ELECTRIC COMPANY, OF SAME PLACE.

DYNAMO-ELECTRIC MACHINE.

SPECIFICATION forming part of Letters Patent No. 587,379, dated August3, 1897.

A li ti fil d-lune 3, 1896. Renewed January 20, 1897. Serial No.619,978. (No model.)

To ctZZ whom it may concern/,-

Be it known that we, ERNEST P. WARNER and HENRY II. XVAIT, citizens ofthe United States, residing at Chicago, in the county of Cook and Stateof Illinois, have invented a certain new and useful Improvement inDynamo-Electric Machines, (Case No. 60,) of which the following is afull, clear, concise, and exact description, reference being had to theaccompanying drawings, forming a part of this specification.

Our invention relates to a dynamo-electric machine; and its object is toprevent the formation of a local magnetic field through the pole-pieces,due to the magnetizing effect of the armature-coils.

In the operation of dynamo-electric ma chines as usually constructed alocal magnetic field is produced in the pole-pieces by thearn'iature-coils, the field passing from the armaturecore across theairspace to the pole-piece, traversing a portion of the polepiece andreturning to the armature-core,thus threading the armature-coils thatare for the instant opposite the pole-piece. This local field interfereswith the proper regulation of the machine; and it is the object of ourinvention to so design the pole-pieces as to prevent the formation ofthe local magnetic field.

0 For this purpose We provide a slot in the face of the pole-pieceextending for a distance into the body thereof, the slot being soproportioned as to form constricted necks or paths, through which thelines of force produced by 3 5 the field coils must pass, the metal ofthe necks being brought to a point near saturation, whereby theproduction of a local magnetic field due to the armaturecoils isprevented.

40 We will describe our invention more in particular by reference to theaccompanying drawings, in which Figure 1 is a diagrammatic viewillustrating the manner in which the field-poles have 5 heretofore beenconstructed, the position of the local magnetic field being indicated bya dotted line. Fig. 2 is a diagrammatic view illustrating thepole-pieces constructed after the manner of our invention, whereby theproduction of a local magnetic field is prevented, is a diagram showingthe pole-piece provided with a number of slots for accomplishing asimilar result. Fig. 4 is a side view of a dynamo-electric machineembodying our invention. Fig. 5 is an end view thereof, partially insection, on line 5 5, Fig.

i. Fig. 6 is a plan view of the machine.

Like letters refer to like parts in the several figures.

As illustrated in Fig. 1, due to the arma- 6o ture-coils a on thearmature-core a, a local magnetic field is produced, threading thearmature-coils which are in front of the polepiece and passing throughthe body of the pole-piece, as indicated by the dotted line a It is theobject of our invention to prevent the formation of this local magneticfield; and to accomplish this object we provide a slot Z) in thepole-piece, the slot being widened at the rear to leave two constrictedpaths b through which the lines of force produced by the field-coils 0must pass in passing to the armature. The cross -sections of the pathsZ2 1) are proportioned so that the metal thereof is brought to a pointnear saturation during the normal operation of the machine, thus chokingback or preventing the passage of the lines of force induced by thecoils a and which tend to find circuit through the metal of thepole-pieces.

In Fig. 3 we have illustrated a pole-piece provided with three slots b12 b narrow at the face of the pole-piece and of increased width at theinterior of the pole-piece, four constricted necks or paths 1)? Z2 b 19being thus 8 provided.

In Figs. 4, 5, and 6 we have illustrated a machine embodying v ourinvention as employed in practice, the machine comprising a standard d,carrying at the top and bottom 0 core-pieces for the field-coils c 0.Upon the ends of the core-pieces are mounted the polepieces ff, betweenwhich rotates the armature g, mounted upon the shaft g, one end of whichis journaled in a standard It, (a portion of which is broken away inFigs. at and 6,) the other end of the shaft g being journaled in abearing mounted upon the standard d. The pole-pieces f f are hollowed orcut away at the middle to leave a thin shell f at the face of thepole-piece. A slot b is provided eX- tending through the shell f asillustrated,

the slot being enlarged at the rear to thus form constricted necks orpaths joining the pole-pieces with the cores upon which the field-coilsare mounted. The lines of force of the field produced by the coils c care thus caused to traverse the constricted necks or paths thus formedin passing to the armature, and in consequence the metal of said necksis brought to a point near saturation, thus preventing the formation ofa local magnetic field through the pole-pieces, due to thearmature-coils that may for the time being rest in front of thepole-pieces.

Bolts i extend through the pole-pieces f f into the cores 6 6, thussecuring the pole-pieces and the cores together. Bolts 1" extend throughthe standard (1 into the cores, thus securing the cores to the standard.Between the edges of the pole-pieces we provide distance-pieces 7t 7c,of non-magnetic material, which serve to support the weight of the upperpole-piece.

Having thus described our invention, what we claim as new, and desire tosecure by Letters Patent, is-

1. In a dynamo-electric machine, the combination with an armature, of apole-piece cut away or slotted to leave constricted necks or paths forthe passage of the main field-lines of force, said necks or paths beingso proportioned that the metal thereof will rise to a pointnearsaturation during the normal operation of the machine to prevent theformation of a local field through the pole-pieces due to the armaturecoils; substantially as described.

2. In a dynamo-electric machine, the combination with cores carrying thefield-coils, the pole-pieces connected therewith by two or moreconstricted necks or paths, said necks or paths being proportioned tocarry the necessary lines of force of the main field when at practicalsaturation-point to thereby prevent the passage of lines of force due tothe armature-coils; substantially as described.

3. Ina dynamo-electric machine, the combination with a pole-piece,provided with a slot or slots, narrow at the pole-face and of increasedwidth at portions removed from the face of the pole-piece, to thus leaveconstricted necks or paths between the face of the pole-piece and theremaining portions 01": the field-magnet circuit to prevent theformation of a local magnetic field; substantially as described.

4. In a dynamo-electric machine, the combination with a standard, ofcores for the field-magnet coils mounted thereon and perpendicularthereto, polepieces mounted upon the ends of said cores, and extendedtoward one another to surround the armature, said pole-pieces beinghollowed or cut away at the middle to leave a thin shell at the face ofthe pole-pieces, a slot extending from the front to the rear of saidshell, said slot being of increased width at the rear to form twoconstricted necks or paths joining the face of the pole-piece with thecore, upon which the fieldmagnet coil is mounted; substantially asdescribed.

In witness whereof we hereunto subscribe our names this 20th day of May,A. D. 1895.

ERNEST P. \VARNER. HENRY II. IVAIT.

Vitnesses:

J OHN W. Smcnun, W. CLYDE JONES.

